Vertically movable door operating means

ABSTRACT

A vertically movable counterbalanced bi-parting door is disclosed which includes a top panel and a bottom panel. The panels are disposed in an access opening having a flat vertically extending door rail disposed at each lateral side. The panels are connected to one another on each lateral side by a cable chain which passes over a sheave, so that the weight of the bottom panel tends to pull the top panel upwardly but is insufficient by itself to do so. The sheave on one side of the door is an idler sheave, and the sheave on the other side of the door is powered by an electric motor to provide the sole applied force to open and close the door. Each lateral side of the top panel is provided with a device for preventing binding of the door in the access opening by accommodating the side thrust loads imposed by the unbalanced force of the powered sheave. The device includes two resilient rollers having an outside diameter not exceeding 1 inch and a hardness not less than 70 nor greater than 80 Shore D durometer hardness which roll on the free edge of the door rail.

United States Patent [191 Peelle, Jr. et a1.

[ Apr. 30, 1974 VERTICALLY MOVABLE DOOR OPERATING MEANS [73] Assignee: The Peelle Company, Bay Shore,

22 Filed: Aug. 23, 1972 21 Appl. No.: 282,922

[52] US. Cl. 49/120 [51] Int. Cl Ed /16 [58] Field of Search 49/120, 119, 425, 366; 160/91 [56] References Cited UNITED STATES PATENTS 910,654 1/1909 Evans 49/120 X 1,416,247 6/1922 Wexler 49/120 X 1,727,399 9/1929 Feldman 49/120 2,286,003 6/1942 Norton et a1. 49/120 X 2,659,939 11/1953 Greig 49/425 2,680,269 6/1954 Watkins 49/425 X 2,834,068 5/1958 Trammell et a1. 49/425 X. 3,252,253 5/1966 Sanders et al. 49/120 3,619,947 11/1971 Burum 49/425 Primary Examiner-Dennis L. Taylor Attorney, Agent, or Firm--McNenny, Farrington, Peame & Gordon ABSTRACT A vertically movable counterbalanced bi-parting door is disclosed which includes a top panel and a bottom panel. The panels are disposed in an access opening having a flat vertically extending door rail disposed at each lateral side. The panels are connected to one another on each lateral side by a cable chain which passes over a sheave, so that the weight of the bottom panel tends to pull the top panel upwardly but is insufficient by itself to do so. The sheave on one side of the door is an idler sheave, and the sheave on the other side of the door is powered by an electric motor to provide the sole applied force to open and close the door. Each lateral side of the top panel is provided with a device for preventing binding of the door in the access opening by accommodating the side thrust loads imposed by the unbalanced force of the powered sheave. The device includes two resilient rollers having an outside diameter not exceeding 1 inch and a hardness not less than 70 nor greater than 80 Shore D durometer hardness which roll on the free edge of the door rail.

14 Claims, 6 Drawing Figures VERTICALLY MOVABLE DOOR OPERATING MEANS BACKGROUND OF THE INVENTION Vertically movable doors, including vertically movable biparting counterbalanced doors, are commonly used in buildings to close access openings such as access openings for freight elevators, dumbwaiters, or conveyors.

Such counterbalanced bi-parting doors include a top panel and a bottom panel which meet approximately at the mid-height of the access opening. The top and bottom panels are connected to one another on each lateral side by a cable chain which passes over a sheave so that the weight of the bottom panel tends to pull the top panel upwardly. The weight of the bottom panel, however, is insufficient by itself to pull the top panel upwardly, so that the door remains closed until an external force is applied to open the door.

The access opening in which such counterbalanced bi-parting doors are used is commonly provided with a generally flat, vertically extending door rail lying in a plane parallel to the plane in which the door is disposed at each lateral side of the door. Each lateral side of the top panel and of the bottom panel of the door is provided with at least one guide shoe which cooperates with the door rail to prevent back-and-forth horizontal movement of the panels in a direction perpendicular to the lateral direction.

Prior to this invention, when such counterbalanced bi-parting doors were power-operated such as by electric motors, it was necessary to apply the force to open and close the door in a manner which would not impose a turning moment on either panel of the door. This was necessary to prevent binding of the door in the access opening because it was not possible to accommodate the side thrust loads imposed by turning moments within the critically small space requirements of an elevator shaft over a satisfactory life span of thousands of cycles. Because it is generally not possible to apply the force at the center of the door due to the small space between the elevator and the building wall, this necessity of avoiding turning moments on the panels of biparting doors has heretofore required that the power to open and close the door be applied to each of the sheaves on the lateral sides of the panels so that an equal force would be applied to each side of the panels through the connecting cable chain.

SUMMARY OF THE INVENTION The present invention overcomes these and other problems of prior art vertically movable doors by providing a vertically movable door upon which the force applied to open and close the door can impose a significant turning moment without binding the door in the access opening-This permits the force to be applied on only one side of the door and eliminates the requirement of providing a drive means on both sides of the door.

In the preferred embodiment, the upper and lower panels of a bi-parting counterbalanced door are disposed for closing an access opening in a substantially vertical wall of a building. A flat vertically extending door rail disposed in a plane parallel to the plane of the upper and lower panels is secured to the wall at each lateral side of the access opening. A flexible cable chain on each lateral side of the panels passes over a rotatable sheave and has one reach connected to the upper panel and the other reach connected to the lower panel so that the weight of the lower panel pulls the upper panel vertically upwardly. The sheave on one lateral side of the door is an idler sheave, and the sheave on the other lateral side of the door is powered by an electric motor to provide the sole applied force to open and close the door.

To prevent binding of the door in the access opening, the invention provides a novel structure which accommodates the side thrust loads imposed on the upper panel over a satisfactory life span and which may be termed a side thrust guide shoe. One such side thrust guide shoe is affixed above the mid-height of the upper panel and one is affixed below the mid-height of the upper panel on each lateral side of the upper panel. Each side thrust guide shoe includes confronting front and rear facing guide pads which cooperate with the oppositely facing sides of the door rail to prevent substantial horizontal movement of the upper panel in a direction perpendicular to the lateral direction.

Each of the side thrust guide shoes also includes two vertically spaced resilient rollers which engage the thin laterally facing free edge of the door rail with rolling contact and provide the sole means for transmitting forces in the lateral direction from the upper panel to the door rail. Each resilient roller has an outside diameter not exceeding 1 inch and a hardness of not less than nor greater than Shore D durometer. In this manner, side thrust loads and shock loads imposed by opening and closing the door are absorbed without damaging the resilient rollers or the thin door rail free edge, and the roller deforms slightly as it is pressed against the free edge of the door rail so that a sufficient contact area between the roller and the door rail edge is presented to prevent skidding of the roller.

The rollers are each rotatably disposed on the side thrust guide shoes intermediate the guide pads and the upper panel, and the length of each roller is greater than the normal distance between the confronting guide pads and preferably at least one and one half times such normal distance. In this manner, the pads provide the sole means to retain the rollers in aligned engagement with the free edge of the door rail and prevent the door rail from slipping off the ends of the rollers after the guide pads have worn substantially.

The rollers are each cast of a pure polyurethane elastomer which has a low unlubricated coefficient of friction so that a bearing is not required between each roller and its associated axle. The axle for each roller is stepped so that the axle may be easily assembled from one side of the side thrust guide shoe and is retained in place when the side thrust guide shoe is secured on the upper panel.

DESCRIPTION OF THE PREFERRED EMBODIMENT These and other aspects and advantages of the invention will become more readily apparent to those skilled in the art upon an understanding of the preferred embodiment of the invention shown in the drawings, wherein:

FIG. 1 is a front elevational view of a wall of a building structure having an elevator access opening which is closed by a bi-parting counterbalanced door;

FIG. 2 is a schematic view of the drive train for applying a force to open and close the bi-parting door shown in FIG. 1;

FIG. 3 is an enlarged, cross-sectional view taken along reference view line 3-3 of FIG. 1;

FIG. 4 is a perspective view of the side thrust guide shoe which is shown in cross section in FIG. 3;

FIG. 5 is a front elevational view of the side guide shoe shown in FIG. 4; and

FIG. 6 is a side elevational view of the side thrust guide shoe shown in FIG. 4.

Referring now to the drawings in greater detail, FIG. 1 shows a vertically movable, bi-parting counterbalanced door 10 disposed in an access opening 11 in a vertically disposed wall 12 of a building structure. The access opening 11 is defined by a right channel jamb 14 at its right lateral side, a left channel jamb 15 at its left lateral side, a channel lintel 16 at its top, and sill 17 at its bottom.

The door 10 includes an upper panel 20 and a lower panel 21, each of which is slidably disposed for biparting vertical movement in a plane parallel to the plane of the wall 12. The upper panel 20 carries a safety seal 22 disposed along its bottom edge, and the panels 20 and 21 meet at the mid-height of the opening 11 when the door is closed.

As shown schematically in FIG. 2, a cable chain 25 on the right lateral side of the door 10 passes over a suitable sheave 26, and one reach of the cable chain 25 is connected'to the right side of the upper panel 20 while the other reach of the cable chain 25 is connected to the right side of the lower panel 21. In a similar manner, a cable chain 27 on the left lateral side of the door 10 passes over a sheave 28 and interconnects the left side of the upper panel 20 and the left side of the lower panel 21.

Prior to the applicants invention, binding of the panels 20 and 21 in the opening 11 was prevented by applying the force to open and close the panels 20 and 21 in a manner such that a turning moment was not imposed on the panels. This was commonly accomplished by driving each of the sheaves 26 and 28 either by sepathrust rate electric motors or by a single motor having a drive train for driving each sheave.

In contradistinction to this prior art structure, the applicants invention solves the problem of preventing binding of bi-parting counterbalanced doors (as well as other types of vertically movable doors) by providing a door in which the force can be applied in a manner which creates a substantial turning moment on the door.This permits the power to be applied to only one side of the door and eliminates the second electric motor or the drive train previously required to apply a balancing force to the other side of the door. As shown schematically in FIG. 2, the sheave 28 on the left side of the door 10 is an idler sheave, while the sheave 26 on the right side of the door 10 is driven by an electric motor 29 so that the sheave 26 provides the sole means for applying a force to open the door 10. In the preferred embodiment, the electric motor 29 has a twospeed motor winding and is incorporated in a single housing with the sheave 26 and is arranged so that the motor 29 can be removed from the sheave 26 for maintenance while the sheave 26 supports the cable chain 25.

As illustrated schematically in FIG. 2, an application of power by the motor 29 to the sheave 26 to open the panels 20 and 21 exerts an unbalanced upward force on the lower right comer of the upper panel 20 by the chain 25 and reduces the force applied at the upper right corner of the panel 21 by the chain 25. This unbalanced force on the panel 20 imposes a turning moment of the panel 20 which tends to turn the panel 20 in the manner shown in phantom in FIG. 2. Similarly, the unbalanced force on the lower panel 21 imposed by reducing the force applied to its upper right corner imposes a turning moment on the panel 21 which tends to turn the panel 21 in the manner shown in phantom in FIG. 2. When the electric motor 29 is reversed to apply power to the sheave 26 in the opposite direction to close the door, the turning moments imposed on the panels 20 and 21 will be opposite the turning moments imposed when the door is opened and will tend to turn the panels 20 and 21 in a direction opposite that shown in phantom in FIG. 2. These turning moments are imposed each time the door 10 is opened and closed and each time the motor 29 changes from low speed to high speed.

To prevent these turning moments from binding the door 10 in the opening 11, the invention provides an apparatus previously unknown in the art which may be termed a side thrust guide shoe. Two such side thrust guide shoes are positioned on each lateral side of the upper panel 20, one above the mid-height of the panel 20 and the other below the mid-height of the panel 20. If desired, side thrust guide shoes may also be provided in a similar manner at each of the four lateral corners of the lower panel 21.

FIGS. 36 show the side thrust guide shoe 30 which is disposed at the lower right lateral side of the panel 20. The side thrust guide shoe 30 is identical to the side thrust guide shoe provided at each of the other locations on the panel 20 described above.

As shown in FIG. 3, a conventional door rail 33 is secured to the right channel jamb 14 by suitable bolts 34. The door rail 33 extends vertically along the channel jamb 14 above the'channel lintel 16 and below the sill 17 a distance sufficient to accommodate full'up ward travel of the panel 20 and full downward travel of the panel 21. Although not shown in the drawings, a similar door rail is also secured to the left channel jamb 15. The door rail 33 includes a generally flat front facing abutment surface 35 and a generally flat rear facing abutment surface 36 which terminate at a free edge 37.

A shoe bar 40 is bolted to the right lateral edge 41 of the upper panel 20, and a similar shoe bar (not shown in the drawings) is bolted to the left lateral edge of the upper panel 20. The shoe bar 40 is a angle and includes a first leg 42 and a second leg 43.

As shown in FIGS. 3-6, the side thrust guide shoe 30 is of any suitable material, such as malleable iron or steel, and includes a generally flat mounting portion 47 which is bolted to the second leg 43 of the shoe bar 40 by suitable bolts 48 which extend through slotted holes 49 in the mounting portion 47. The side thrust guide shoe 30 also includes a backing portion 50 which is provided with suitable threaded holes for receiving Allen-head adjustment screws 51. The adjustment screws 51 act against the first leg 42 of the shoe bar 40 to provide lateral adjustment of the side thrust guide shoe 30 toward and away from the free edge 37 of the door rail 33. The bolts 48 are loosened for such lateral adjustment and are tightened after such adjustment has been made to retain the side thrust guide shoe 30 in its proper position.

A first guide portion 55 and a second guide portion 56 extend in a direction generally parallel to one another, and provide forwardly and rearwardly facing confronting guide pads 57 and 58, respectively. As shownin FIG. 3, the guide pads 57 and 58 receive the door rail 33 therebetween and cooperate with the abutment surfaces 35 and 36, respectively, of the door rail 33 to prevent back and forth horizontal movement of the upper panel 20 in a direction perpendicular to the lateral direction.

The side thrust guide shoe 30 is also provided with a first roller 61 and a second roller 62 rotatably disposed on axles 63 and 64, respectively, in a cavity 65 defined by reduced thickness portions of the guide portions 55 and 56. As best shown in FIGS. 3 and 6, each axle 63, 64 includes a large diameter portion which is received with a slide fit in a larger diameter hole in the first guide portion 55 and a smaller diameter portion which is received with a slide fit in a smaller diameter hole in the second guide portion 56. In this manner, the axles 63 and 64 may be assembled prior to mounting the side thrust guide shoe 30 on the shoe bar 40, and the second leg 43 of the shoe bar 40 retains the axles 63 and 64 in place.

The rollers 61 and 62 are each no greater than one inch in outside diameter to meet the critical space requirements of the elevator shaft in which they are diposed. The rollers 61 and 62 are of pure cast polyurethane elastomer having a hardness of not less than 70 nor greater than 80 durometer on the Shore D scale. The outside diameter of this material resists tearing, cuts and abrasions from rolling on the rough and thin free edge 37 of the door rail 34. The rollers 61 and 62 have a low unlubricated coefficient of friction so that a bearing between the rollers and the axles is not required. This further reduces the space requirements of each roller. A polyurethane elastomer with these properties is commercially available from E. l. DuPont de Nemours & Co. of Wilmington, Delaware under the trademark Adiprene.

The side thrust guide shoe 30 in cooperation with the other side thrust guide shoes, not shown in the drawings but affixed to the upper panel 20 in the manner described above, prevent binding of the upper panel 20 as it is opened and closed. This is accomplished by the rollers 61 and 62 engaging the free edge 37 of the door rail 33 with rolling contact to provide the sole means for transmitting forces in the lateral direction from the upper panel 20 to the door rail 33. Because the rollers 61 and 62 have an outside diameter no greater than one inch and a hardness no less than 70 nor greater than 80 durometer on the Shore D scale, the side thrust loads imposed by the turning moments tending to bind the door in the opening slightly flatten the portion of the outside diameter of the rollers 61 and 62 which confronts the edge 37. This provides a sufficient surface contact area with the edge 37 to force the rollers 61 and 62 to roll and prevents skidding.

As shown in FIGS. 3 and 4, the rollers 61 and 62 are disposed intermediate the guide pads and the upper panel, and the guide pads 5 7 and 58 are enlarged thickness end portions of the guide portions 55 and 56. The length of the rollers 61 and 62 is greater than the normal distance between the confronting guide pads 57 and 58 and is preferably at least one and one half times such normal distance and two and one half times the width of the edge portion 37. In this manner, the guide pads 57 and 58 provide the sole means for maintaining the rollers 61 and 62 in aligned confronting relation to the edge 37 so that the door rail 34 cannot slip past the end of the rollers 61 or 62. Additionally, such confronting relation is maintained even after the pads have worn substantially.

Although a preferred embodiment of the invention has been shown and described in detail, various modifications and rearrangements may be made without departing from the scope of the invention as defined by the claims.

What is claimed is:

' 1. In a building structure having an access opening in a substantially vertical wall and a vertically extending door rail on each lateral side of said access opening secured to said wall, a vertically movable bi-parting counterbalanced door for closing said access opening; said bi-parting counterbalanced door comprising an upper panel and a lower panel disposed between said door rails, flexible cable means on each lateral side of said panels, each of said cable means passing over a sheave and having one reach connected to said upper panel and the other reach connected to said lower panel so that the weight of said lower panel pulls said upper panel vertically upwardly, one of said sheaves being an idler sheave, the other of said sheaves being driven by an electric motor and providing the sole force to open and close said door, two guide shoes on each lateral side of said upper panel cooperating with said door rail for limiting horizontal movement of said upper panel in a direction perpendicular to the lateral direction, one of said two guide shoes being spaced above the midheight of said upper panel and the other of said two guide shoes being spaced below the midheight of said upper panel on each lateral side of said upper panel, at least one resilient roller carried by each of said guide shoes, said rollers rolling on the free edge of said door rail and providing the sole means for transmitting forces in said lateral direction from said upper panel to said door rail, said guide shoes each including substantially parallel confronting guide pads for receiving said door rail therebetween and for engaging opposite sides of said door rail for limiting said horizontal movement of said upper panel in said perpendicular direction, the length of said rollers being greater than the normal distance between said confronting guide pads, and said confronting guide pads providing the sole means for maintaining said rollers in confronting aligned relation with said door rail edge.

2. A bi-parting counterbalanced door as set forth in claim 1, wherein said length of said rollers is greater than one and one half times said normal distance between said confronting guide pads. 3. A bi-parting counterbalanced door as set forth in claim 1, wherein said rollers each have an outside diameter not exceeding 1 inch and a hardness not less than Shore D durometer nor greater than Shore D durometer.

4. A bi-parting counterbalanced door as set forth in claim 1, wherein said rollers are each rotatably disposed on said guide shoes between said guide pads and said upper panel.

5. A bi-parting counterbalanced door as set forth in claim 4, wherein said guide shoes each include two generally flat parallel guide portions, said guide pads each being an elongated surface of one of said guide portions, said guide portions each including a reduced thickness portion defining a cavity for holding said rollers, and the length of each of .said rollers disposed in said cavity being greater than the normal distance between said confronting guide pads.

6. A bi-parting counterbalanced door as set forth in claim wherein said length of said rollers is at least one and one half times said normal distance between said confronting guide pads.

7. A bi-parting counterbalanced door as set forth in claim 5, including a shoe bar on each lateral edge of said upper panel, said shoe bar having a first leg parallel to said lateral edge of said upper panel and a second leg extending laterally substantially perpendicular to said first leg and said guide shoes being mounted on said shoe bars.

8. A bi-parting counterbalanced door as set forth in claim 7, wherein said rollers are each disposed on an axle, said axles each includes a larger diameter portion extending through a larger diameter hole in one of said reduced thickness portions and a smaller diameter portion extending through a smaller diameter hole in the other of said reduced thickness portions, and one of said legs of said shoe bar retaining said axle in said reduced thickness portion.

9. In a building structure having an access opening in a substantially vertical wall and a vertically extending door rail on each lateral side of said access opening securedto said wall, a vertically movable door; said vertically movable door including at least one vertically movable panel disposed between said door rails and at least one side thrust guide shoe on each lateral side of said panel, said side thrust guide shoes each including two substantially flat parallel guide portions for receiving said door rail therebetween and for engaging opposite sides of said door rail for limiting horizontal movement of said panel in a direction perpendicular to the lateral direction, at least one resilient roller rotatably disposed between said parallel guide portions, said roller rolling on the free edge of said door rail and providing the sole means for transmitting forces in the lateral direction from said panel to said door rail, said parallel guide portions each including a reduced thickness portion intermediate said door rail and said panel, said reduced thickness portions defining a cavity, said roller being rotatably disposed in said cavity, and the length of said roller being greater than the normal distance between the portions of said guide portions which engage said door rail.

10. A vertically movable door as set forth in claim 9 wherein said length of said roller is greater than one and one half times said normal distance between said portions which engage said door rail.

11. A vertically movable door as set forth in claim 9 wherein said rollers are each rotatably disposed on an axle extending between said reduced thickness portions.

12. A vertically movable door as set forth in claim 9 wherein said rollers each have an outside diameter not exceeding 1 inch and a hardness not less than Shore D durometer nor greater than Shore D durometer.

13. A vertically movable door as set forth in claim 9 wherein two resilient rollers are rotatably disposed between said parallel guide portions in positions of vertically spaced adjacency.

14. In a building structure having an access opening in a substantially vertical wall and a vertically extendin'g door rail on each lateral side of said access opening secured to said wall, a vertically movable door; said vertically movable door including at least one vertically movable panel disposed between said door rails, a shoe bar on each lateral edge of said panel having a first leg parallel to said lateral edge and a second leg extending laterally substantially perpendicular to said first leg, and at least one side thrust guide shoe on each lateral side of said panel, said side thrust guide shoes each including two substantially flat parallel guide portions for receiving said door rail therebetween and for engaging opposite sides of said door rail for limiting horizontal movement of said panel in a direction perpendicular to the lateral direction, at least one resilient roller rotatably disposed on an axle between said parallel guide portions, said axles each including a larger diameter portion received with a slide fit in a larger diameter hole in one of said parallel guide portions and a smaller diameter portion received with a slide fit in a smaller diameter hole in the other of said guide portions, said side thrust guide shoes being mounted on said shoe bars, and said second legs of said shoe bars retaining said axles in said guide portions. 

1. In a building structure having an access opening in a substantially vertical wall and a vertically extending door rail on each lateral side of said access opening secured to said wall, a vertically movable bi-parting counterbalanced door for closing said access opening; said bi-parting counterbalanced door comprising an upper panel and a lower panel disposed between said door rails, flexible cable means on each lateral side of said panels, each of said cable means passing over a sheave and having one reach connected to said upper panel and the other rEach connected to said lower panel so that the weight of said lower panel pulls said upper panel vertically upwardly, one of said sheaves being an idler sheave, the other of said sheaves being driven by an electric motor and providing the sole force to open and close said door, two guide shoes on each lateral side of said upper panel cooperating with said door rail for limiting horizontal movement of said upper panel in a direction perpendicular to the lateral direction, one of said two guide shoes being spaced above the midheight of said upper panel and the other of said two guide shoes being spaced below the midheight of said upper panel on each lateral side of said upper panel, at least one resilient roller carried by each of said guide shoes, said rollers rolling on the free edge of said door rail and providing the sole means for transmitting forces in said lateral direction from said upper panel to said door rail, said guide shoes each including substantially parallel confronting guide pads for receiving said door rail therebetween and for engaging opposite sides of said door rail for limiting said horizontal movement of said upper panel in said perpendicular direction, the length of said rollers being greater than the normal distance between said confronting guide pads, and said confronting guide pads providing the sole means for maintaining said rollers in confronting aligned relation with said door rail edge.
 2. A bi-parting counterbalanced door as set forth in claim 1, wherein said length of said rollers is greater than one and one half times said normal distance between said confronting guide pads.
 3. A bi-parting counterbalanced door as set forth in claim 1, wherein said rollers each have an outside diameter not exceeding 1 inch and a hardness not less than 70 Shore D durometer nor greater than 80 Shore D durometer.
 4. A bi-parting counterbalanced door as set forth in claim 1, wherein said rollers are each rotatably disposed on said guide shoes between said guide pads and said upper panel.
 5. A bi-parting counterbalanced door as set forth in claim 4, wherein said guide shoes each include two generally flat parallel guide portions, said guide pads each being an elongated surface of one of said guide portions, said guide portions each including a reduced thickness portion defining a cavity for holding said rollers, and the length of each of said rollers disposed in said cavity being greater than the normal distance between said confronting guide pads.
 6. A bi-parting counterbalanced door as set forth in claim 5 wherein said length of said rollers is at least one and one half times said normal distance between said confronting guide pads.
 7. A bi-parting counterbalanced door as set forth in claim 5, including a shoe bar on each lateral edge of said upper panel, said shoe bar having a first leg parallel to said lateral edge of said upper panel and a second leg extending laterally substantially perpendicular to said first leg and said guide shoes being mounted on said shoe bars.
 8. A bi-parting counterbalanced door as set forth in claim 7, wherein said rollers are each disposed on an axle, said axles each includes a larger diameter portion extending through a larger diameter hole in one of said reduced thickness portions and a smaller diameter portion extending through a smaller diameter hole in the other of said reduced thickness portions, and one of said legs of said shoe bar retaining said axle in said reduced thickness portion.
 9. In a building structure having an access opening in a substantially vertical wall and a vertically extending door rail on each lateral side of said access opening secured to said wall, a vertically movable door; said vertically movable door including at least one vertically movable panel disposed between said door rails and at least one side thrust guide shoe on each lateral side of said panel, said side thrust guide shoes each including two substantially flat parallel guide portionS for receiving said door rail therebetween and for engaging opposite sides of said door rail for limiting horizontal movement of said panel in a direction perpendicular to the lateral direction, at least one resilient roller rotatably disposed between said parallel guide portions, said roller rolling on the free edge of said door rail and providing the sole means for transmitting forces in the lateral direction from said panel to said door rail, said parallel guide portions each including a reduced thickness portion intermediate said door rail and said panel, said reduced thickness portions defining a cavity, said roller being rotatably disposed in said cavity, and the length of said roller being greater than the normal distance between the portions of said guide portions which engage said door rail.
 10. A vertically movable door as set forth in claim 9 wherein said length of said roller is greater than one and one half times said normal distance between said portions which engage said door rail.
 11. A vertically movable door as set forth in claim 9 wherein said rollers are each rotatably disposed on an axle extending between said reduced thickness portions.
 12. A vertically movable door as set forth in claim 9 wherein said rollers each have an outside diameter not exceeding 1 inch and a hardness not less than 70 Shore D durometer nor greater than 80 Shore D durometer.
 13. A vertically movable door as set forth in claim 9 wherein two resilient rollers are rotatably disposed between said parallel guide portions in positions of vertically spaced adjacency.
 14. In a building structure having an access opening in a substantially vertical wall and a vertically extending door rail on each lateral side of said access opening secured to said wall, a vertically movable door; said vertically movable door including at least one vertically movable panel disposed between said door rails, a shoe bar on each lateral edge of said panel having a first leg parallel to said lateral edge and a second leg extending laterally substantially perpendicular to said first leg, and at least one side thrust guide shoe on each lateral side of said panel, said side thrust guide shoes each including two substantially flat parallel guide portions for receiving said door rail therebetween and for engaging opposite sides of said door rail for limiting horizontal movement of said panel in a direction perpendicular to the lateral direction, at least one resilient roller rotatably disposed on an axle between said parallel guide portions, said axles each including a larger diameter portion received with a slide fit in a larger diameter hole in one of said parallel guide portions and a smaller diameter portion received with a slide fit in a smaller diameter hole in the other of said guide portions, said side thrust guide shoes being mounted on said shoe bars, and said second legs of said shoe bars retaining said axles in said guide portions. 